The Collaborative International Dictionary
Underlease
Underlease \Un"der*lease\, n. (Law)
A lease granted by a tenant or lessee; especially, a lease
granted by one who is himself a lessee for years, for any
fewer or less number of years than he himself holds; a
sublease.
--Burrill.
Wiktionary
underlease
n. (context legal English) A lease granted by a tenant or lessee; a sublease.